At 22.33 and 22.38 hours on 27 Oct 1942, U-509 fired torpedoes at convoy SL-125 northwest of the Canary Islands and hit the Pacific Star and Stentor.

The Stentor (Master William Williams) in station #91 was carrying the Vice Commodore (Capt Richard Hart Garstin, CBE, RNR) and six naval staff members, a crew of 107 and seven gunners (the ship was armed with one 4in, one 20mm and four machine guns), one DBS and 124 passengers, mostly service personnel, including 26 army personnel and 11 nursing sisters. The ship was hit by one torpedo on the starboard side at the bulkhead between holds #2 and #3. The palm oil stored in the deep tank was thrown up by the explosion and immediately caught fire, pouring into the passengers accommodation and setting the forward holds and bridge on fire. The men on the bridge were either killed or badly burned and had to be assisted to reach their lifeboat stations, but the ship suddenly sank by the bow about 8 minutes after being hit and the boat carrying the injured master capsized, drowning almost all occupants. Three lifeboats had been destroyed or were on fire, so the survivors abandoned ship in the remaining four boats and rafts. Three hours after the ship sank, HMS Woodruff (K 53) (A/LtCdr F.H. Gray, RNR) began picking up survivors, disrupting the rescue work for several minutes after mistaking the sound of the motor boat for that of a U-boat and continuing throughout the night until 202 survivors were picked up. The master, the Vice Commodore 19 crew members, one naval staff member and 22 passengers, including three army personnel and four nurses were lost. Three days later, the overcrowded corvette transferred 100 survivors to HMS Ramsey (G 60) (LtCdr R.B. Stannard, VC, RNR) which took them to Liverpool, while the remaining survivors were landed at Milford Haven on 6 November.

The ship’s surgeon William Chisholm was posthumously awarded the Albert Medal. He attended to the badly injured Vice Commodore and deliberately sacrificed his chance of safety by remaining with him until the ship sank.